Interelectronic-interaction correction of first order in [Formula Presented] is studied for radiative recombination of an electron with a heavy He-like ion in the ground state. A rigorous relativistic treatment is compared with two frequently applied approximations. A calculation is carried out for radiative recombination of an electron into [Formula Presented] [Formula Presented] and [Formula Presented] states of He-like uranium for impact energies between 10 and 700 MeV/u.